BREEDING ECOLOGY OF THE ROYAL TERN (THALASSEUS MAXIMUS) AT ISLA EL RANCHO, MEXICO: COLONY SIZE AND NEST LOCATION AFFECT PREDATION

作者：Angulo Gastelum Ulises T^*; Alfredo Castillo Guerrero Jose; Mellink Eric

来源：Ornitologia Neotropical, 2011, 22(1): 131-142.

• Breeding success
• colony size
• coloniality
• seabirds
• Royal Tern
• Thalasseus maximus

We studied the nesting biology of the Royal Tern (Thalasseus maximus) in a large (c. 1500 nests) and a small colony (c. 300 nests), at Isla El Rancho, Sinaloa, Mexico, during the 2007 breeding season. We measured egg volume, nest density, and distance to the edge of the colony, and investigated their effects on hatching and fledging success. We evaluated also egg predation by the Heermann's Gull (Laws heermanni). Colony size, nesting density, location within the colony, predation by gulls, and a possible food shortage affected breeding success. Nesting density was higher in the centre of colonies (9.57 nests/m(2) +/- 0.28) than at the periphery (8.20 +/- 0.34), and higher in the large colony (9.24 +/- 0.21) than in the small one (6.66 +/- 0.66). Hatching success was higher in the large colony (82.5%) than in the small one (50%), and in central areas than at the periphery. Both colonies attracted similar numbers of Hoermann's Gulls, but these predated eggs at a higher rate in the small (0.54 eggs/h +/- 0.11) than in the large colony (0.25 eggs/h +/- 0.06), and focused predation attempts at the periphery. This highlights the importance of colony size and nest location in protecting against predation in Royal Terns. Similar to other tern studies, egg predation was the main cause of reproductive failure, suggesting that in Royal Terns this is a major selective pressure that contributes to the maintenance of coloniality and regulates minimum colony size. Accepted 23 February 2011.

• 出版日期2011